The present invention relates to a cleaning apparatus and a cleaning method for an image forming apparatus such as an electronic copying machine according to an electrophotographic system, which has a cleaning device and forms an electrostatic latent image on a photosensitive drum to produce an image.
In the prior art, charging is effected on a photosensitive drum in an electronic copying machine, a latent image on the photosensitive drum is developed using toner, the developed toner image is transferred on transfer paper, and the charge on the photosensitive drum is erased.
After the toner image has been transferred on the transfer paper, a slight amount of toner and a slight amount of paper dust remain on the surface of the photosensitive drum. To remove them, a cleaning device is provided.
A cleaning mechanism conventionally known as a cleaning device for removing the toner and paper dust comprises a roll-shaped electrically conductive brush, provided on the downstream side of a transfer/separation charger, and an elastic cleaning blade provided on the downstream side of the electrically conductive brush.
The toner and paper dust remaining on the surface of the photosensitive drum after the transfer is partly removed by the electrically conductive brush and then further removed by the cleaning blade put in contact with the surface of the photosensitive drum.
Depending on the amount of toner removed by the electrically conductive brush (roller), the edge portion of the cleaning blade may apply a great stress on the photosensitive drum, and removal of the paper dust may be more difficult than that of toner. To solve this problem, a power supply applies a bias voltage, which is of an opposite polarity to the electricity of paper dust, to the electrically conductive brush, whereby the paper dust is electrostatically removed by the electrically conductive brush before it reaches the cleaning blade.
However, another power supply is required for a bias to be applied to the electrically conductive brush. This results in an increase in cost. In addition, in a case where a voltage level at the time of turn-on of bias is always constant, the removal performance for residual toner and paper dust varies depending on the potential level of the photosensitive drum at the position of the electrically conductive brush. Thus, there is a problem with the compatibility of removal performances of both cleaning mechanisms.
Specifically, if the toner removal performance is too good under the condition that the electrically conductive brush is grounded, no toner will reach the edge portion of the cleaning blade in the next step and this will lead to excessive friction of the edge portion. Furthermore, flaws will easily occur on the surface of the photosensitive drum due to positively (+) charged paper dust on the negatively (xe2x88x92) charged surface of the photosensitive drum.
If a fixed bias voltage (xe2x88x92) is applied to the electrically conductive brush by the external power supply and the removal performance level for toner (xe2x88x92) is lowered, the toner removal performance of the electrically conductive brush at the time of total-surface printing is considerably degraded.
The object of the present invention is to provide a cleaning device and a cleaning method for an image forming apparatus, which can stably maintain the performance of removing residual toner and paper dust.
In order to achieve the object, there is provided a cleaning device for removing toner and paper dust remaining on a photosensitive drum in an image forming apparatus which forms an image using the photosensitive drum, the cleaning device comprising: a first removing section which is grounded via a non-linear resistor element and removes toner and paper dust remaining on a surface of the photosensitive drum; and a second removing section which, following the first removing section, removes the toner and paper dust remaining on the surface of the photosensitive drum.
There is also provided a cleaning method for removing toner and paper dust remaining on a photosensitive drum in an image forming apparatus which forms an image using the photosensitive drum, the method comprising: removing toner and paper dust remaining on a surface of the photosensitive drum, using a roll-shaped electrically conductive brush grounded via a varistor; and removing the toner remaining on the surface of the photosensitive drum, which still remains after the removal, using a cleaning blade formed of an elastic material.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.